/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.coyote.ajp;

import org.apache.tomcat.util.buf.ByteChunk;
import org.apache.tomcat.util.buf.CharChunk;
import org.apache.tomcat.util.buf.MessageBytes;
import org.apache.tomcat.util.res.StringManager;

/**
 * A single packet for communication between the web server and the container.
 * Designed to be reused many times with no creation of garbage. Understands the
 * format of data types for these packets. Can be used (somewhat confusingly)
 * for both incoming and outgoing packets.
 * 
 * @author Henri Gomez
 * @author Dan Milstein
 * @author Keith Wannamaker
 * @author Kevin Seguin
 * @author Costin Manolache
 */
public class AjpMessage {

	protected static org.apache.juli.logging.Log log = org.apache.juli.logging.LogFactory
			.getLog(AjpMessage.class);

	/**
	 * The string manager for this package.
	 */
	protected static StringManager sm = StringManager
			.getManager(Constants.Package);

	// ------------------------------------------------------------ Constructor

	public AjpMessage(int packetSize) {
		buf = new byte[packetSize];
	}

	// ----------------------------------------------------- Instance Variables

	/**
	 * Fixed size buffer.
	 */
	protected byte buf[] = null;

	/**
	 * The current read or write position in the buffer.
	 */
	protected int pos;

	/**
	 * This actually means different things depending on whether the packet is
	 * read or write. For read, it's the length of the payload (excluding the
	 * header). For write, it's the length of the packet as a whole (counting
	 * the header). Oh, well.
	 */
	protected int len;

	// --------------------------------------------------------- Public Methods

	/**
	 * Prepare this packet for accumulating a message from the container to the
	 * web server. Set the write position to just after the header (but leave
	 * the length unwritten, because it is as yet unknown).
	 */
	public void reset() {
		len = 4;
		pos = 4;
	}

	/**
	 * For a packet to be sent to the web server, finish the process of
	 * accumulating data and write the length of the data payload into the
	 * header.
	 */
	public void end() {
		len = pos;
		int dLen = len - 4;

		buf[0] = (byte) 0x41;
		buf[1] = (byte) 0x42;
		buf[2] = (byte) ((dLen >>> 8) & 0xFF);
		buf[3] = (byte) (dLen & 0xFF);
	}

	/**
	 * Return the underlying byte buffer.
	 */
	public byte[] getBuffer() {
		return buf;
	}

	/**
	 * Return the current message length. For read, it's the length of the
	 * payload (excluding the header). For write, it's the length of the packet
	 * as a whole (counting the header).
	 */
	public int getLen() {
		return len;
	}

	/**
	 * Add a short integer (2 bytes) to the message.
	 */
	public void appendInt(int val) {
		buf[pos++] = (byte) ((val >>> 8) & 0xFF);
		buf[pos++] = (byte) (val & 0xFF);
	}

	/**
	 * Append a byte (1 byte) to the message.
	 */
	public void appendByte(int val) {
		buf[pos++] = (byte) val;
	}

	/**
	 * Append an int (4 bytes) to the message.
	 */
	public void appendLongInt(int val) {
		buf[pos++] = (byte) ((val >>> 24) & 0xFF);
		buf[pos++] = (byte) ((val >>> 16) & 0xFF);
		buf[pos++] = (byte) ((val >>> 8) & 0xFF);
		buf[pos++] = (byte) (val & 0xFF);
	}

	/**
	 * Write a MessageBytes out at the current write position. A null
	 * MessageBytes is encoded as a string with length 0.
	 */
	public void appendBytes(MessageBytes mb) {
		if (mb == null) {
			log.error(sm.getString("ajpmessage.null"),
					new NullPointerException());
			appendInt(0);
			appendByte(0);
			return;
		}
		if (mb.getType() == MessageBytes.T_BYTES) {
			ByteChunk bc = mb.getByteChunk();
			appendByteChunk(bc);
		} else if (mb.getType() == MessageBytes.T_CHARS) {
			CharChunk cc = mb.getCharChunk();
			appendCharChunk(cc);
		} else {
			appendString(mb.toString());
		}
	}

	/**
	 * Write a ByteChunk out at the current write position. A null ByteChunk is
	 * encoded as a string with length 0.
	 */
	public void appendByteChunk(ByteChunk bc) {
		if (bc == null) {
			log.error(sm.getString("ajpmessage.null"),
					new NullPointerException());
			appendInt(0);
			appendByte(0);
			return;
		}
		appendBytes(bc.getBytes(), bc.getStart(), bc.getLength());
	}

	/**
	 * Write a CharChunk out at the current write position. A null CharChunk is
	 * encoded as a string with length 0.
	 */
	public void appendCharChunk(CharChunk cc) {
		if (cc == null) {
			log.error(sm.getString("ajpmessage.null"),
					new NullPointerException());
			appendInt(0);
			appendByte(0);
			return;
		}
		int start = cc.getStart();
		int end = cc.getEnd();
		appendInt(end - start);
		char[] cbuf = cc.getBuffer();
		for (int i = start; i < end; i++) {
			char c = cbuf[i];
			// Note: This is clearly incorrect for many strings,
			// but is the only consistent approach within the current
			// servlet framework. It must suffice until servlet output
			// streams properly encode their output.
			if ((c <= 31) && (c != 9)) {
				c = ' ';
			} else if (c == 127) {
				c = ' ';
			}
			appendByte(c);
		}
		appendByte(0);
	}

	/**
	 * Write a String out at the current write position. Strings are encoded
	 * with the length in two bytes first, then the string, and then a
	 * terminating \0 (which is <B>not</B> included in the encoded length). The
	 * terminator is for the convenience of the C code, where it saves a round
	 * of copying. A null string is encoded as a string with length 0.
	 */
	public void appendString(String str) {
		if (str == null) {
			log.error(sm.getString("ajpmessage.null"),
					new NullPointerException());
			appendInt(0);
			appendByte(0);
			return;
		}
		int len = str.length();
		appendInt(len);
		for (int i = 0; i < len; i++) {
			char c = str.charAt(i);
			// Note: This is clearly incorrect for many strings,
			// but is the only consistent approach within the current
			// servlet framework. It must suffice until servlet output
			// streams properly encode their output.
			if ((c <= 31) && (c != 9)) {
				c = ' ';
			} else if (c == 127) {
				c = ' ';
			}
			appendByte(c);
		}
		appendByte(0);
	}

	/**
	 * Copy a chunk of bytes into the packet, starting at the current write
	 * position. The chunk of bytes is encoded with the length in two bytes
	 * first, then the data itself, and finally a terminating \0 (which is
	 * <B>not</B> included in the encoded length).
	 * 
	 * @param b
	 *            The array from which to copy bytes.
	 * @param off
	 *            The offset into the array at which to start copying
	 * @param numBytes
	 *            The number of bytes to copy.
	 */
	public void appendBytes(byte[] b, int off, int numBytes) {
		if (pos + numBytes + 3 > buf.length) {
			log.error(sm.getString("ajpmessage.overflow", "" + numBytes, ""
					+ pos), new ArrayIndexOutOfBoundsException());
			if (log.isDebugEnabled()) {
				dump("Overflow/coBytes");
			}
			return;
		}
		appendInt(numBytes);
		System.arraycopy(b, off, buf, pos, numBytes);
		pos += numBytes;
		appendByte(0);
	}

	/**
	 * Read an integer from packet, and advance the read position past it.
	 * Integers are encoded as two unsigned bytes with the high-order byte
	 * first, and, as far as I can tell, in little-endian order within each
	 * byte.
	 */
	public int getInt() {
		int b1 = buf[pos++] & 0xFF;
		int b2 = buf[pos++] & 0xFF;
		return (b1 << 8) + b2;
	}

	public int peekInt() {
		int b1 = buf[pos] & 0xFF;
		int b2 = buf[pos + 1] & 0xFF;
		return (b1 << 8) + b2;
	}

	public byte getByte() {
		byte res = buf[pos++];
		return res;
	}

	public byte peekByte() {
		byte res = buf[pos];
		return res;
	}

	public void getBytes(MessageBytes mb) {
		int length = getInt();
		if ((length == 0xFFFF) || (length == -1)) {
			mb.recycle();
			return;
		}
		mb.setBytes(buf, pos, length);
		pos += length;
		pos++; // Skip the terminating \0
	}

	/**
	 * Copy a chunk of bytes from the packet into an array and advance the read
	 * position past the chunk. See appendBytes() for details on the encoding.
	 * 
	 * @return The number of bytes copied.
	 */
	public int getBytes(byte[] dest) {
		int length = getInt();
		if (pos + length > buf.length) {
			log.error(sm.getString("ajpmessage.read", "" + length));
			return 0;
		}

		if ((length == 0xFFFF) || (length == -1)) {
			return 0;
		}

		System.arraycopy(buf, pos, dest, 0, length);
		pos += length;
		pos++; // Skip terminating \0
		return length;
	}

	/**
	 * Read a 32 bits integer from packet, and advance the read position past
	 * it. Integers are encoded as four unsigned bytes with the high-order byte
	 * first, and, as far as I can tell, in little-endian order within each
	 * byte.
	 */
	public int getLongInt() {
		int b1 = buf[pos++] & 0xFF; // No swap, Java order
		b1 <<= 8;
		b1 |= (buf[pos++] & 0xFF);
		b1 <<= 8;
		b1 |= (buf[pos++] & 0xFF);
		b1 <<= 8;
		b1 |= (buf[pos++] & 0xFF);
		return b1;
	}

	public int getHeaderLength() {
		return 4;
	}

	public int getPacketSize() {
		return buf.length;
	}

	public int processHeader() {
		pos = 0;
		int mark = getInt();
		len = getInt();
		// Verify message signature
		if ((mark != 0x1234) && (mark != 0x4142)) {
			log.error(sm.getString("ajpmessage.invalid", "" + mark));
			if (log.isDebugEnabled()) {
				dump("In: ");
			}
			return -1;
		}
		if (log.isDebugEnabled()) {
			log.debug("Received " + len + " " + buf[0]);
		}
		return len;
	}

	/**
	 * Dump the contents of the message, prefixed with the given String.
	 */
	public void dump(String msg) {
		if (log.isDebugEnabled()) {
			log.debug(msg + ": " + buf + " " + pos + "/" + (len + 4));
		}
		int max = pos;
		if (len + 4 > pos)
			max = len + 4;
		if (max > 1000)
			max = 1000;
		if (log.isDebugEnabled()) {
			for (int j = 0; j < max; j += 16) {
				log.debug(hexLine(buf, j, len));
			}
		}
	}

	// ------------------------------------------------------ Protected Methods

	protected static String hexLine(byte buf[], int start, int len) {
		StringBuffer sb = new StringBuffer();
		for (int i = start; i < start + 16; i++) {
			if (i < len + 4) {
				sb.append(hex(buf[i]) + " ");
			} else {
				sb.append("   ");
			}
		}
		sb.append(" | ");
		for (int i = start; i < start + 16 && i < len + 4; i++) {
			if (!Character.isISOControl((char) buf[i])) {
				sb.append(new Character((char) buf[i]));
			} else {
				sb.append(".");
			}
		}
		return sb.toString();
	}

	protected static String hex(int x) {
		String h = Integer.toHexString(x);
		if (h.length() == 1) {
			h = "0" + h;
		}
		return h.substring(h.length() - 2);
	}

}
